1. Field of the Invention
The present invention relates to an optical switch for use in fiber communication and optical network technology, and particularly to a mechanical optical switch with three reflecting surfaces as a switching element.
2. Description of Related Art
Optical signals are commonly transmitted in optical fibers, which provide efficient light channels through which the optical signals can pass. Recently, optical fibers have been used in various fields, including telecommunications, where light passing through an optic fiber is used to convey either digital or analog information. Efficient switching of optical signals between individual fibers is necessary in most optical processing systems or networks to achieve the desired routing of the signals.
In fiber optic systems, various methods have been previously developed for switching optical signals between fiber cables. In these previously developed methods, one important category is mechanical optical switch.
Mechanical optical switches come in two different designs: where the optical components move, and where the fibers move. Factors for assessing the capability of an optical switch include low insertion loss ( less than 1 dB), good isolation performance ( greater than 50 dB) and bandwidth capacity compatible with optical fibers.
Moving fiber switches involve the actual physical movement of one or more of the fibers to specific positions to accomplish the transmission of a beam of light from one fiber end to another under selected switching conditions. Moving optical component switches, on the other hand, include optical collimating lenses which expand the beam of light from the fibers, and then, using moving prisms or mirrors, reswitch the expanded beam as required by the switching process.
The moving fiber switches have a stringent tolerance requirement for the amount and direction of fiber movement. The tolerance is typically of a small portion of the fiber core diameter for two fibers to precisely align to reduce loss. The fibers themselves are quite thin and may be subject to breakage if not properly protected. On the other hand, reinforcing the fibers with stiff protective sheaths makes the fibers less flexible, increasing the force required to manipulate each fiber into alignment. Thus these moving fiber optical switches share a common problem of requiring high precision parts to obtain precise positioning control and low insertion loss. This results in high costs and complicated manufacture of the switches. Moreover, frequently moving fibers to and fro is apt to damage or even break the fibers.
The moving optical component switches have less stringent movement control tolerance requirements because of the collimating lenses.
For example, referring to FIG. 10, U.S. Pat. No. 5,436,986 discloses a mechanical optical switch comprising a first and second input fibers 101, 103, a first and second output fibers 102, 104, a driving device 304 and a mirror assembly 200. The mirror assembly 200 includes a moveable block 203 and two mirrors 201, 202 assembled to the block 203. Each mirror has two reflecting surfaces for reflecting light signals from the input fibers 101, 103. The driving device 304 drives the mirror assembly 200 to move between a first position and a second position. When the mirror assembly 200 is in the first position, light signals from the first and second input fibers 101, 103 are directly transmitted to the corresponding second and first output fibers 104, 102. When the mirror assembly 200 is displaced to the second position, the mirror 201 reflects the light signals from the first input fiber 101 to the mirror 202, and then the mirror 202 reflects the light signals to the first output fiber 102; the mirror 202 reflects the light signals from the second input fiber 103 to the mirror 201, and then the mirror 201 reflects the light signals to the second output fiber 104. In this mechanical optical switch, when in the second position the light signals are reflected two times, which increases the difficulties of precise alignment between the input fibers 101, 103, mirrors 201, 202 and the output fibers 102, 104.
As illustrated in FIG. 11, U.S. Pat. No. 5,742,712 describes another mechanical optical switch, which relies on a moveable mirror 520 having two opposite reflecting surfaces being moved into an optical path between a first and second fixed collimating lenses 528, 536. When the moveable mirror 520 is displaced out of the optical path, the light signals from a first and second input fibers 522, 530 are directly transmitted to a corresponding second and first output fibers 532, 524. However, when the moveable mirror 520 is moved into the optical path, the signals from the first and second input fibers 522, 530 are reflected to the corresponding first and second output fibers 524, 532.
In this mechanical optical switch, the insertion of the mirror 520 will introduce an insertion loss between the input fibers 522, 530 and the output fibers 524, 532 attributable to a thickness between the two opposite reflecting surfaces of the moveable mirror 520.
For the above reasons, an improved optical switch is desired. In particular, an optical switch is desired which has high optical efficiency, is easy to align, and does not require movement of the optical fibers themselves.
An object of the present invention is to provide an optical switch which is easy to align and has a low insertion loss.
Another object of the present invention is to provide an optical switch which uses three reflecting surfaces as a switching element.
An optical switch in accordance with the present invention comprises a first collimator retaining a first input fiber and a second output fiber, a second collimator retaining a first output fiber and a second input fiber, a switching element, a driving device, a moveable arm, a moveable block, a base and two supporting elements assembled onto the base for fixing the first and second collimators thereon.
The switching element comprises a reflector assembly and a third reflector. The reflector assembly is mounted on the moveable block and includes a first reflector and a second reflector. The third reflector is fixed on the base and can reflect light from the first collimator to the second collimator.
The driving device drives the moveable arm to move the reflector assembly fixed on the moveable block between a first position and a second position. When in the first portion, the first and second reflectors reflect light from the first input fiber to the second output fiber, and from the second input fiber to the first output fiber, respectively. When the reflector assembly is in the second portion, the third reflector reflects light from the first input fiber to the first output fiber, and from the second input fiber to the second output fiber.
Other objects, advantages and novel features of the invention will become more apparent from, the following detailed description when taken in conjunction with the accompanying drawings.